Security always requires a multi-layered scheme. SSH is a good example of this. Methods range from simple sshd configuration through the use of PAM to specify who can use SSH, to application of port-knocking techniques, or to hide the fact that SSH access even exists. Applying these techniques can make life much harder for possible intruders, who will have to go past three unusual barriers.

Bazaar is used to produce the Ubuntu Linux distribution, which is an enormous software project with thousands of components. If you're using a UNIX or Linux system, chances are that your distribution offers a pre-built Bazaar package. Bazaar is flexible enough to accommodate Subversion - a centralized system and Git - a decentralized system. This article introduces you to Bazaar's many appealing features.

As the kernel and user space exist in different virtual address spaces, there are special considerations for moving data between them. Explore the ideas behind virtual address spaces and the kernel APIs for data movement to and from user space, and learn some of the other mapping techniques used to map memory.

Python programmers shouldn't get too smug. While many people agree that Python is designed in a way that makes it a highly readable language, there can still be problems with legacy, untested Python code too. Porting legacy Perl to Python can be a daunting task. In this article, learn some of the theory behind dealing with legacy code, including what not to do.

The IBM AIX operating system provides a highly scalable IT infrastructure for client workloads. Learn about the latest version, AIX 7.1, an open standards-based UNIX operating system, that includes significant new capabilities for virtualization, security features, availability features, and manageability.

"Learn about the latest version of AIX 7.1 - an open standards-based UNIX operating system"

PowerHA for AIX is the new name for HACMP (High Availability Cluster Multiprocessing). HACMP is an application that makes system fault resilient and reduces downtime of applications. This article introduces PowerHA and provides a detailed explanation of how to configure a two node cluster. This document is very useful for understanding PowerHA and setting up a two node cluster.

Learn how to check the integrity of your Linux filesystems, monitor free space, and fix simple problems. Use the material in this article to study for the Linux Professional Institute (LPI) 101 exam for Linux system administrator certification or just to check your filesystems and keep them in good working order, especially after a system crash or power loss. Today's world relies heavily on technology, and at times technology can fail us. That is why, unlike traditional methods of storage such as office cabinets, it would be necessary to back up your electronic file systems.

Ksplice applies kernel patches on-the-fly - no reboot required — in a fraction of a second. Here's a hands-on guide to performing painless system updates. Learn how to patch a live kernel and give reboots the boot.

Amaze your friends with cool vi tips and tricks that will improve the efficiency of your file editing. This article takes you through ten of the less well-known vi commands that should form part of any serious vi user's toolkit.

"L2ARC is a new layer between Disk and the cache (ARC) in main memory for ZFS. It uses dedicated storage devices to hold cached data. The main role of this cache is to boost the performance of random read workloads. The intended L2ARC devices include 10K/15K RPM disks like short-stroked disks, solid state disks (SSD), and other media with substantially faster read latency than disk."

The GNU Image Manipulation Program (GIMP) is a robust application for editing and manipulating digital images. In this article, you will learn how to get started with the GIMP code, how to build the project from the Git repositories, and how to find your way around the code tree. And you will build an example application that creates a whole new painting tool for the program.

"Dive into the code base of the GNU Image Manipulation Program and add to it"

Java language is the tool of choice for Android developers. The Android runtime uses its own virtual machine, Dalvik, which is not the usual Java virtual machine that most Java developers are used to. In this article you will learn advanced Java features and how they are implemented on Android. This includes features such as concurrency, networking, and database access.

In Part 1 learn to Install and configure a simple cluster and discover ways to monitor and manage Hadoop using its core Web interfaces. In Part 2 Install configure a multinode cluster and dig into the management aspects of Hadoop.